Blow molding bottles made of polyethylene naphthalate (PET) resin (i.e. plastic bottles) have many excellent characteristics and therefore are widely used as bottle containers. Such containers are typically molded by injection molding a preform into a bottomed cylindrical shape and then stretch molding the preform to an expanded shape after heating to a temperature at which an expansion effect can be achieved.
In other words, as illustrated in FIG. 12 (corresponding to FIG. 12 of Patent Literature 1), preform 31 heated to a temperature at which an expansion effect is achieved is inserted into a blow mold 101, with a mouth tube section 32 of the preform 31 projecting upwards and with a neck ring 33, circumferentially provided integrally at the lower edge of the outer peripheral surface of the mouth tube section 32, engaged with a neck support flange 103. With a guide tube 110, which is the tip of a blow nozzle 104, being loosely inserted into the mouth tube section 32 of the preform 31, the preform 31 is stretched in the axial direction by a stretching rod 108 inserted through an insertion hole 111 formed by penetrating through the center of the blow nozzle 104 and is stretched in the radial direction by air, which is a pressurized fluid, blown through the insertion hole 111. A bottle 41 is thus molded.
Patent Literature 2 discloses an invention related to a method for blow molding preform using liquid instead of blown air as the pressurized fluid. If the content fluid that is ultimately filled into the product, such as a drink, cosmetic, medicine, or the like, is used as the liquid, then this method for molding allows for omission of the filling step and thus simplifies the production line.